Irrigation Run Time Calculator

Find how long to run sprinklers for target watering.

Target watering depth

Sprinkler precip rate

in/hr

Area watered(optional)

sq ft

Results update as you type.

Run time

—

Water used—

How it works

Watering the right amount keeps lawns and gardens healthy without wasting water, and this calculator finds how long to run your sprinklers. You enter the target watering depth, your sprinkler system's precipitation rate, and optionally the area watered, and it returns the run time in minutes and the total gallons used. The logic is simple: if you want to apply one inch of water and your sprinklers deliver two inches per hour, you run them for half an hour. Most lawns need roughly one to one and a half inches of water per week, including rainfall, delivered in one or two deep sessions rather than frequent light ones, which encourages deep roots and drought tolerance. You can find your system's precipitation rate with the catch-cup test: place several containers around the zone, run it for a set time, and measure the average depth collected. Different sprinkler types vary widely, from under half an inch per hour for drip and rotors to two inches or more for spray heads. Watering early in the morning reduces evaporation and disease. Enter your target depth, precipitation rate, and area to find your ideal run time.

Formula

Run time (min) = (target depth ÷ precip rate) × 60

The run time equals the target watering depth divided by the sprinkler's precipitation rate, converted to minutes by multiplying by 60. The water used is the area times the depth times 0.623 gallons per square foot per inch, giving the total volume applied during that run.

Source:Irrigation scheduling

We review all our tools from time to time to ensure accuracy.

Worked example

Target watering depth:1Sprinkler precip rate:2Area watered:500

(1 ÷ 2) × 60 = 30 minutes; about 311 gallons over 500 sq ft.

How to use this calculator

1
Enter your values
Enter target watering depth and sprinkler precip rate.
2
Adjust the options
Adjust area watered if they apply — sensible defaults are already set.
3
Read your result
Run time updates instantly as you type — no button to press.

Frequently asked questions

How long should I run my sprinklers?

Divide the target watering depth by your sprinkler's precipitation rate and multiply by 60 for minutes. To apply one inch with a system delivering two inches per hour, run it 30 minutes. Deep, infrequent watering is better than short daily runs because it encourages deep roots and makes the lawn more drought-resistant.

How do I find my sprinkler's precipitation rate?

Use the catch-cup test: place several straight-sided containers, like tuna cans, evenly across the zone, run the sprinklers for a set time such as 15 minutes, then measure the average water depth in the cans and scale it to an hourly rate. This real-world measurement is more accurate than manufacturer specs, which vary with pressure and layout.

How much water does a lawn need?

Most lawns need about one to one and a half inches of water per week, including rainfall, to stay healthy. In hot, dry weather they may need more, and cool or rainy periods less. Splitting this into one or two deep waterings rather than daily sprinkles builds deeper roots and a hardier, more drought-tolerant lawn.

When is the best time to water?

Early morning, roughly between 4 and 10 a.m., is ideal because cooler temperatures and calm air minimize evaporation, and leaves dry during the day, reducing fungal disease. Watering midday wastes water to evaporation, while evening watering leaves grass wet overnight, encouraging disease. A morning schedule delivers the most water to the roots efficiently.

Why water deeply but less often?

Frequent shallow watering keeps roots near the surface where soil dries fast, making the lawn weak and thirsty. Deep, infrequent watering soaks the soil so roots grow downward chasing the moisture, producing a stronger lawn that withstands heat and drought. This is why a longer run every few days beats a short run every day for most established lawns.